With the quick development of mobile internet and the increasing popularization of smart terminals, requirements of users on data transmission rate and user experience become increasingly higher. In order to improve user experience and system throughput, especially in order to improve throughput of hotspot areas, networking architecture of a heterogeneous network is put forward, i.e., a plurality of low-power small base stations are placed in an area covered by a macro base station, and the macro base station and the small base stations jointly form the heterogeneous network; and in other words, a great amount of small cells are deployed in an area covered by a macro cell, wherein the macro base station corresponds to the macro cell and the small base stations correspond to the small cells.
The dense deployment of the small cells is an effective mechanism for improving a network capacity and reducing coverage holes. However, it also causes the problems of serious interference between cells and energy consumption increase of the cells. For the reason, a small cell on/off technical solution is put forward. The small cell on/off technical solution can adaptively control on/off of the small cells. For example, under the situation that the small cells have no demand on UE connection or service, the small cells can be turned off to reduce the interference with neighboring cells while the power consumption can be reduced.
When the small cell on/off technical solution is adopted, in other words, in an application scenario of small cell on/off, UE resides in a serving cell, supposing that the UE resides in a small cell 1 or a macro cell; simultaneously, the UE still searches for other neighboring small cells, supposing that the other small cell which is searched out is a small cell 2; here, the UE is in an RRC_CONNECTED state, and in other words, the UE is in a state in which information sent by the serving cell can be received in real time; and the searched other small cells may be in an on state and may also be in an off state. Under this circumstance, the serving cell of the UE, i.e., the small cell 1 or the macro cell does not know time of transmission between the UE and the small cell 2, the serving cell of the UE also does not know precise time for the small cell 2 sending a discovery time, and thus the serving cell of the UE cannot inform of the UE the precise time for the small cell 2 sending the discovery signal. A signal transmission delay and a sending delay of the discovery signal sent by the small cell 2 cause that signals received by the UE from the serving cell and the small cell 2 are not synchronized. As a result, a searching window becomes larger, the discovery delay becomes greater, consequently the processing implementation of signals received by the UE is complicated and the power consumption of the UE is increased accordingly.